US Patent 7940544 Memory system having multiple vias at junctions between traces

An improvement to a memory system having a hierarchical bitline structure wherein traces that form global write lines are connected to each other using junctions that include multiple vias to reduce capacitance and increase yield. At least one of a pair of traces connected by the vias includes a widened portion that provides sufficient overlap with the other trace to allow the two or more vias to be formed between the traces at the overlap. Parallel traces for global write lines that carry a write signal and its inverse may be positioned more than one maximum-density grid space apart to allow the widened portions to be formed between the traces. A global read line that is formed in a different metal layer from the global write line traces may be positioned in a grid space between the global write line traces to reduce the capacitance of this line.